In the process of fabricating a display panel, exposure by a mask is an important step. Exposure is not only one of the most sophisticated steps in liquid crystal display panel fabrication, but also one of the steps of the highest device investment and operating costs. Therefore, reducing fabrication cost and improving device productivity by reducing the number of times of using the mask and exposing are always a kind of exploration in display panel fabrication.
Conventional Twist Nematic (TN) type display panel includes an array substrate. As illustrated in FIG. 1 and FIG. 2, the array substrate of the TN-type display panel comprises: a transparent substrate 1, and a first metal layer, a gate insulating layer 7, an active layer 8, a second metal layer, a passivation layer 9 and a transparent conductive layer sequentially disposed on the transparent substrate 1. The first metal layer includes a gate line 2 and a gate electrode 31, the second metal layer includes a data line 4, a source electrode 32 and a drain electrode 33; and the transparent conductive layer includes a pixel electrode 5. As illustrated in FIG. 1, the gate line 2 and the data line 4 are arranged intersecting with each other, and a thin film transistor 3 and the pixel electrode 5 are formed in the region enclosed by the gate line 2 and the data line 4. The array substrate further comprises a gate line terminal region and a data line terminal region which are disposed at the edge of the array substrate and are used for connecting circuit boards, as illustrated in FIG. 3, the gate line 2 in the gate line terminal region bb′ is connected to the circuit board through a via-hole disposed in the gate insulating layer 7 and the passivation layer 9 thereon, the data line 4 in the data line terminal regions cc′ is connected to the circuit board through a via-hole disposed in the passivation layer 9 thereon, and a voltage input of the gate line and the data line is controlled by the circuit board.
In the fabrication process of the array substrate in the prior art, each of the first metal layer, the passivation layer and the pixel electrode layer is formed via one exposure by using a normal mask; the active layer and the second metal layer are formed via one exposure by using a half-tone or a half-gray mask. That is, four times of exposure are needed, which requires more frequent exposure, longer fabrication cycle and higher costs.